Also known as: mental disease or defect · mental disease · mental defect · insanity defense · lack of criminal responsibility
Written by attorneys · grounded in primary & secondary sources — see below
An affirmative defense to criminal liability that excuses a defendant from responsibility for conduct when, as a result of mental disease or defect, the defendant lacked substantial capacity either to appreciate the criminality or wrongfulness of the conduct or to conform the conduct to the requirements of law. The defense does not encompass an abnormality manifested only by repeated criminal or antisocial conduct.
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Maurice Marshall, diagnosed with severe schizophrenia, deliberately set fire to a vacant warehouse after weeks of delusional beliefs that the building housed government surveillance equipment. Medical records confirmed that the delusions directly drove the arson. The court acquitted Marshall because the offense would not have occurred but for his mental disease.
Mariam Mansour remained silent after receiving Miranda warnings when asked about prior mental health treatment. At trial she raised an insanity defense based on bipolar disorder. The prosecutor attempted to use her silence to argue the defense was fabricated, but the court sustained the objection and barred the argument.
Miranda Morales faced capital murder charges after killing her roommate during a psychotic episode. Her defense introduced expert testimony that bipolar disorder substantially impaired her capacity to appreciate wrongfulness. The jury considered the evidence and imposed life imprisonment rather than death.
Meredith Maxwell was indicted for embezzlement and waited until after discovery closed to file written notice of an insanity defense. She cited recent hospitalization but offered no explanation why the records could not have been obtained earlier. The court denied leave to file late and precluded the defense at trial.
Musa Mensah was acquitted of assault after proving that schizophrenia caused him to attack a stranger he believed was an alien. The court immediately ordered commitment to a state mental health facility for custody, care, and treatment rather than release.
Michelle Murphy, an indigent defendant charged with murder, made a preliminary showing that she would rely on an insanity defense. The court ordered the state to provide access to a psychiatrist to assist in preparing the defense and to testify at sentencing regarding future dangerousness.
The defendant must prove that at the time of the conduct, as a result of mental disease or defect, the defendant lacked substantial capacity either to appreciate the criminality or wrongfulness of the conduct or to conform the conduct to the requirements of law. The defense excludes abnormalities shown only by repeated criminal or antisocial conduct.
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…or would gravely impair the physical or mental health of the mother, (ii) that the child would be born with grave physical or mental defect, or (iii) that the pregnancy resulted from rape or incest, or illicit intercourse with a girl under the age of 16 years]. "SECTION 2. [ Penalty. ] Any person who performs or procures an…
…was ratified. Commonwealth v. York , 50 Mass. 93 (1845).[^maj-8] In 1895 the common-law view was abandoned with respect to the insanity defense in federal prosecutions. Davis v. United States , 160 U. S. 469 (1895). This ruling had wide impact on the practice in the federal courts with respect to the burden of proving various…
…either so deficient that he has no will, no conscience, of controlling mental power, or if, through the overwhelming violence of mental disease
…Majority opinion · [^maj- ] [^maj-1]: The statute provides: [^maj-2]: Petitioner initially filed a notice of intent to rely on "mental disease or defect
…proceedings against Ake. At a pretrial conference in June, Ake’s attorney informed the court that his client would raise an insanity defense. To enable him to prepare and present such a
A defendant must notify the government in writing within the time for filing pretrial motions or at a later time set by the court. Failure to provide timely notice bars reliance on the defense unless the court finds good cause for a late filing.
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The court must order the defendant committed to the custody of the Commissioner of Mental Hygiene for placement in an appropriate institution for custody, care, and treatment. Release requires a later judicial determination that the person poses no danger to self or others.
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No. Once Miranda warnings are given, the government implicitly assures the suspect that silence carries no penalty. Using post-warning silence as evidence to undermine an insanity claim violates due process.
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Yes. When a jury or court may recommend death or imprisonment, evidence that mental disease or defect impaired the defendant's capacity to appreciate wrongfulness or conform conduct to law is admissible in favor of a sentence of imprisonment.
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